Apparatus for expanding metallic tubular workpieces



A ril 25, 1939. B BANNISTER 2,155,883 APPARATUS FOR EXPANDING METALLIC TUBULAR WORKPIECES I Filed Feb. 11, 1937 FIGZ).

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Patented Apr. 25,1939

UNITED STATES PATENT OFFICE TUBULAR. WORKPIECES Bryant Bannister, Mount Lebanon, Pa, assignor to National Tube Company, a corporation of New Jersey Application February 11, 1937, Serial No. 125,327

1 Claim.

This invention relates to the manufacture of pipes and tubes and more particularly to an apparatus for expanding metallic tubular workpieces.

The customary manner of expanding tubular work-pieces, particularly the larger sizes of from 14" to 26" in diameter, has been in a mill composed of two conical rolls, or disks, that compress the metal of the work-piece against a' conical mandrel, or plug, disposed therebetween and control the increase in diameter by controlling the reduction of wall-thickness. Thusylf it is desired to increase the diameter of a tubular work-piece by a certain percentage, the wall-thickness of the work-piece entering the mill has a thickness greater than that of the outgoing shell by an amount equal to the desired percentage increase in diameter, and as the work-piece advances helically through the expanding pass, the profile of the mandrel with respect to the rolls or disks, is such that wall reductions are made, causing a proportionate increase in diameter. In this type of pass, the guides employed perform the function of merely steadying the work-piece and do not, to any appreciable extent, control the perimeter of the expanding work-piece at any point.

Moreover, since the perimeter of the tubular work-piece is not confined, practically all of the metal displaced flows circumierentially to produce an increase in diameter as'there is no natural tendency to increase the length of the expanding shell, although in many'cases it is desirable. Some increase in length may, according to prior art practice, he produced by making a disproportionate wall reduction at the gorge of the pass, but since the action which produces this increase in length is concentrated at the entry of the pass, and not in the expanding portion, such action produces excessive wear on both the mandrel and the rolls, and materially impedes the forward travel of the work-piece.

A further disadvantage of the priorart practice is that the expansions throughout the bass are unregulated and cause the perimeter of the work-piece, at any section of the pass, to vary with variations in the entering wall and temperature of the metal, and thereby deviate from. a true cone. This changes the speed relationship -'between the rolls, or disks, and thecone at that point, and this change in speed relationship can only be ofiset by slippageand twisting of the work-piece. The combined results of these efiects are upsetting of the metal, excessive twist in the work-piece which causes severe tearing of the work-piece at the end, mixing it dimcult to further process the work-piece and resulting in a large loss of material due to the amount which must be severed in the finishing operations. It is also apparent that in this prior art method of expanding tubular work-pieces, the cross-section thereof, particularly at the outlet end 01' the pass, is far from circular and is, in fact, almost rectangular. This form of section is difficult to rotate without rupturing the metal, and greatly limitsthe thinness of wall that can be produced.

In accordance with the teachings of the present invention, the diameter of a tubular workpiece is controlled by the use of guides which confine the expanding portion thereof and maintain it substantially conical in shape throughout the pass. In this way the tubular work-piece is substantially circular in cross-section at any point in the pass and "any excess metal which is displaced by the action of the rolls in conjunction with the mandrel, and which normally would produce an increase in diameter, is forced by the guides into an increase in length. Accordingly,

the pass may be designed to effect an increase in eter, compensate forirregularities in the wall of the entering work-piece, and, in addition to this, produce an increase in length.

It is accordingly an object of the present invention to provide an improved apparatus for expanding metallic tubular workepieces which will elimite the disadvantages previously mentioned.

foregoing and further objects will be apparent after referring to the drawing in which:

Fl 1 is a frantary plan of a conventional pipe or tube mill with the guide devices removed; I his 2 is an enlarged fragmentary sectional elevation of the guide devices of the present invention in operative position; and I Figure 3 is a sectional view on the line m-m of Figure 2. I

Referring more particularly to the drawing, the letter A designates a pair of cone-sha metal-working rolls, either or both of which are driven by a suitable source of power (not shown) In order to secure a forward feeding of the workpiece, the rolls A are disposed with their axes of rotation oppositely inclined to each other with respect to the horizontal, or the equivalent arrangement whereby the axes of rotation are in parallel planes to each other and parallel to the axis of the work-piece but equidistant above and below the plane of the axis of the work-piece. Suitably positioned between the rolls A is a n drel plug B which is cone-shaped and has a ,A and plug B are parallel. It will be noted that the length of the pass 4' between the gorge 2 and the end 3 of the reducing zone permits a gradual reduction of the wall-thickness of the workpiece 0.

Positioned between the rolls A are a pair of stationary work-piece guides In. These guides l0 have concave surfaces I I disposed adjacent the plug B which are in the form of a section of the perimeter of a cone, the divergence from the center axis of which corresponds to the decrease in diameter of the rolls A. Consequently, when the guides I!) are placed adjacent the plug B a substantially conical-shaped pass is defined by the rolls A, plug B and guides I0.

In operation, it will be seen that the perimeter of the tubular work-piece C will be confined to substantially the shape of a true cone as it progresses through the pass and will be circular in cross-section at any point in the pass. By so confining the perimeter of the work-piece, a considerable increase in length is produced simultaneously with the-increase in diameter.

In actual practice it has been shown that this controlled pass permits the: rolling of gauges 25 to 30% lighter than has heretofore been commercially feasible and that delivery speeds out of the mill are approximately 50% greater than in conventional mills. Furthermore, it has been shown that the power required in the expanding operation is materially reduced while the life of the mandrel plug, guides and rolls has been considerably extended.

While I have shown and described one specific embodiment of my invention, it will be understood that -I do not wish to be limited exactly thereto since various modifications may be made without departing from the scope of the invention as defined by the following claim.

I claim:

Apparatus for expanding metallic tubular work-pieces comprising, in combination, at least two coacting power-actuated conical metalworking rolls, said metal-working rolls having divergent axes and being constructed and arranged to provide divergent metal-working surfaces of substantial length, a mandrel plug disposed intermediate said metal-working rolls, said mandrel plug having a truly frusto-conical working surface, a stationary guide disposed intermediate said metal-working rolls and above the line of pass defined thereby, and a stationary guide disposed intermediate said metal-working rolls and below said line of pass, the guiding surfaces of said stationary guides being closely disposed with respect to said metal-working rolls and'coextensive with the length of the metalworking portion of the pass defined by the metalworking surfaces of said metal-working rolls and the truly frusto-conical working surface of said mandrel, said guiding surfaces being constructed and arranged to conform to segments of frustocones having substantially the same divergence as the metal-working surfaces of said metalworking rolls.

BRYANT BANNIS'I'ER. 

